In April of last year, Troy Guard, owner of TAG and TAG Raw Bar in Larimer Square, became an operating partner of Madison Street, a Congress Park neighborhood restaurant and lounge that Joe Vostrejs, COO of Larimer Associates, took over in the fall of 2010. The space, a former Dominos Pizza, didn't come easy, thanks to a vocal minority who, incredulously, were concerned that a new joint from one of the most successful restaurant groups in town -- a restaurant that would replace a big-name lackluster chain -- would somehow sully the vibrant enclave that already thrives with merchants, bars and restaurants.

Not surprisingly, Vostrejs and his team prevailed, and Madison Street quickly found its niche, offering a relaxed oasis in which to grab a burger and a beer with friends. And the burgers, which Vostrejs described as "killer" when I interviewed him last year, took off, in part thanks to Guard, who, despite his Asian focus at TAG and TAG Raw Bar, makes some of the best burgers in the city, including ones that defy tradition; his kangaroo burger, for example, is in a league of its own.

And Vostrejs and Guard, who have been around the block enough times to know what diners want in their bellies, came to the conclusion that the Congress Park 'hood liked burgers, and last month, they made the decision to transition from Madison Street to TAG Burger Bar, which will debut tomorrow. "Madison Street was doing great," says Guard, "but the investors and I looked at what was selling, and what was selling the most was burgers, so we wanted to concentrate on what our guests wanted -- plus I've always wanted to do a burger joint," he adds.

But this isn't your run-of-the-mill meat market. The burgers -- classic beef, lamb, bison, turkey, housemade veggie or Skuna Bay salmon -- are served with either a Bluepoint Bakery bun or naked, with butter lettuce, and they're topped with everything from burrata to green papaya slaw. And the classic beef burger is a proprietary blend of brisket, chuck and short rib created exclusively for the restaurant.

But it's the Andrew Jackson burger -- a showstopper that arrives crowned with house-cured pork belly, a fried egg, truffled aioli mustard-vinegar slaw, bone-marrow salt and crisp chicken skin -- that will undoubtedly turn heads. Leave it to Guard, who's renowned for thinking way beyond the ordinary, to create something extraordinary, and vegetarians might say the same thing about the meatless burger, an offbeat -- and delicious -- blend of chick peas, edamame beans, red onions, oregano, tahini and quinoa that may even persuade carnivores to forgo meat, at least temporarily.

And he didn't stop there: The menu also boasts baked potatoes, which you can get traditionally "loaded" or topped with the same ingredients that crown the burgers. There's the "Godzilla," for example, a combination of teriyaki sauce, shiitake mushrooms, crisped tempura flakes and smoked kewpi, or the "Ménage à trois" with Gruyere, French onion soup "onions" and Grey Poupon. Essentially, "you pick your protein, your packaging -- bun or lettuce -- and your style, which can also be loaded on a burger or a baked potato," says Guard, whose menu also includes house-brined pickles, housemade kimchi and several variations of fries, one of which comes strewn with Cheez Whiz and pico de gallo.

And the space, which has been revamped, mimics the new menu. Guard hired a couple of local artists to graffiti one wall, a bold, abstract conversation piece that's hued red, bright green and black. "I always wanted to have graffiti in a restaurant," he says, and "the artists came up with a really creative, fun, whimsical and crazy design that's really cool." There's a mural, too, on the patio, created by the same designers, that's just as striking, and TAG, Guard's bulldog, is at the center of the action. The dining room is also bedecked with new leather booths, and the bar now trots out milkshakes, both benign and with booze. In fact, there's a whole shelf devoted to nothing more than milkshake marvels: Whoppers, candy corn, peppermints, M&M's and just about every other candy you can think of.

"I'm not trying to reinvent the wheel," stresses Guard, "but I do want to have some fun with the menu and with our drinks, and I think the neighborhood is going to really like what we're doing."

And that will include lunch, which, along with dinner, will be served seven days a week, and in November, TAG Burger Bar will add a happy hour menu, too. Brunch will continue on Saturday and Sunday with the same menu from its days of Madison Street.

I stopped by Tag Burger Bar last week to get a sneak peek of the menu and the space, the photos of which are on the following pages. Be hungry.